Doug Wildey: Twisted Tales #3 original art (1983)
John Cullen Murphy: Big Ben Bolt original art (1959)
Steve Ditko & Eric Stanton: Merry Mixup, the Madcap Model original art.
Though signed only by Stanton, the lettering and (at least) the faces are definitely Ditko.
Gray Morrow: original art from The Illustrated Roger Zelazny (1978)
Alan Kupperberg (pencils) & John Romita (inks): Amazing Spider-Man Sunday strip (1979)
Hal Foster: Tarzan original art (1936)
(Source: All Star Auctions)
Howard Chaykin: The Shadow original art (1986)
Nick Cardy: Columbo painting
Nick Cardy: “Manhattan, NY” (1939)
Hugo Pratt: convention sketch (1972)